In general, the relation between an input and an output of an internal interleaver of a turbo encoder follows the below equation when inputs are C0, C1, C2, . . . Ck−1 and outputs are C′0, C′1, C′2, . . . C′k−1.C′i=C′Π(i), i=0, 1, 2, . . . K−1
Further, indexes of an input stream and an output stream follow the below equation.Π(i)=(f1*i+f2*i2)modK 
FIG. 1 is a diagram illustrating an apparatus 100 for generating an internal interleaver index of a conventional turbo encoder.
Referring to FIG. 1, the apparatus 100 for generating the internal interleaver index of the conventional turbo encoder includes a first multiplier 110, an adder 120, a second multiplier, and a divider 140.
The apparatus 100 for generating the internal interleaver index of the conventional turbo encoder receives inputs of K, which is a size of input data, f1 and f2 calculated from K, and a value of i according to an order of bits and outputs II(i) satisfyingΠ(i)=(f1*i+f2*i2)modK. 
The first multiplier 110 receives inputs of f2 and i and outputs a value of f2*i.
The adder 120 receives inputs of i and f2*i output through the first multiplier 110 and outputs a value of f2*i+f1.
The second multiplier 130 receives inputs of i and f2*i+f1 output through the adder 120 and outputs a value of (f2*i+f1)*i.
The divider 140 receives inputs of K and (f2*i+f1)*i, performs (f2*i+f1)*i/K, and then outputs (f2*i+f1)*imodK corresponding to the remainder.
The apparatus 100 for generating the internal interleaver index of the conventional turbo encoder outputs the index in the unit of bits, so that the time for generating the index is increased in proportion to the size of the input data. As a result, the performance of the apparatus is deteriorated.
Further, there is a problem in that the apparatus 100 for generating the internal interleaver index of the conventional turbo encoder requires the multiplier and the divider, which have high importance in an aspect of the hardware implementation, in order to generate the index.